Good Question, Brian,
All too often people plant trees either too close together or too close to a home.
The species of tree you are planning to plant needs to be of concern.
As well, try to have some idea where water lines, electrical lines are etc.
Planting trees on your property is an investment of which can reward you for years and even generations to come. The best "rule of thumb" is plant as far away as possible. My original answer to you is too long to publish here... email me at firstname.lastname@example.org for more